Printing method for use with dot printer

ABSTRACT

A printing method to increase the printing speed of a dot printer. Before printing on the basis of the dot data representative of an original dot pattern showing fonts, graphics end the like, the original dot pattern is converted by converting M (M≧3) dots successive in the line direction into N (M&gt;N≧2, M≠2N) dots. Then, printing is performed on the basis of the thus converted dot data. In a modification, conversion is performed by converting each dot into n (n≧2) successive intermediate dots in the line direction and when 2n or more intermediate dots are successive, selecting every m{(2n-1)≧m≧(n+1) }-th intermediate dot. In another modification, pattern conversion is effected by converting each dot into n(n≧2) successive intermediate dots, in a zone where printing is possible at the same dot interval as that of the original dot pattern, selecting only dots out of the intermediate dots that are arranged at the same dot interval as that of the original dot pattern, and in the other zone, selecting every m{(2n-1)≧m≧(n+1) }-th intermediate dot.

This is a division of application Ser. No. 08/190,770, filed Feb. 2,1994, which is a continuation of application Ser. No. 07/985,519 filedDec. 2, 1992, now abandoned which is a continuation of Ser. No.07/697,125 filed May 8, 1991, now abandoned which is a division of Ser.No. 07/622,992 filed Dec. 6, 1990, now abandoned.

This invention relates to a printing method for use with dot printers.

BACKGROUND OF THE INVENTION

Hitherto, to attain high-speed printing using a wire dot printer, forexample, a method was known (see, for example, Japanese Patent Laid-OpenNo. 60-73852) which comprised the steps of generating a secondary dotpattern from an original dot pattern showing fonts and the like byremoving every other dot from the original dot pattern, and scanning aprint head on the basis of the secondary dot pattern at a speed 2 timesfaster than usual to attain printing.

According to the method comprising the steps of converting the originaldot pattern into the secondary dot pattern by removing every other dotout of the original dot pattern and performing printing on the basis ofthe secondary dot pattern, although the printing speed is doubled, thethus printed dot pattern is significantly distorted as compared with theoriginal dot pattern, resulting in a poor quality of printing.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a printing methodfor use with a dot printer which can increase the printing speed withlittle deterioration in printing quality.

To accomplish the foregoing object, the present invention provides aprinting method which comprises the steps of receiving the dot datarepresentative of an original dot pattern showing fonts, graphics andthe like; converting the pattern of the original dot pattern byconverting M(M≧3) successive dots in the line direction to N(M>N≧2,M≠2N) dots; and performing printing on the basis of the thus converteddot data. Specifically, printing is performed while scanning a printhead at a speed faster than usual, or printing is performed whilescanning the print head at a speed M/N times faster than usual. In amodification, the foregoing object can also be accomplished by aprinting method which comprises the steps of receiving the dot datarepresentative of an original dot pattern showing fonts, graphics andthe like; converting the pattern of the original dot pattern byconverting each dot to n(n≧2) intermediate successive dots in the linedirection and when 2n or more intermediate dots are successive,selecting every m{(2n-1)≧m≧(n+1)}-th intermediate dot; and performingprinting on the basis of the thus converted dot data. Specifically,printing is performed while scanning a print head at a speed faster thanusual. In another modification, the foregoing object can also beaccomplished by a printing method which comprises the steps of receivingthe dot data representative of an original dot pattern showing fonts,graphics and the like; when printing is to be performed at a speedfaster than the moving speed of a print head attained when the originaldot pattern is printed, converting the pattern of the original dotpattern by converting each dot into n(n≧2) successive intermediate dots,in a zone where printing is possible at the same dot interval as that ofthe original dot pattern, selecting only dots from the intermediate dotsthat are arranged at the same dot interval as that of the original dotpattern, and in the other zone, selecting every m{(2n-1)≧m≧(n+1)}-thintermediate dot; and performing printing on the basis of the thusconverted dot data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a system according to the presentinvention;

FIG. 2 is a flowchart showing a first operation mode of the system shownin FIG. 1;

FIGS. 3A-3B are diagrams explanatory of the first operation mode of thesystem shown in FIG. 1;

FIG. 4 is a diagram showing a printed example based on an original dotpattern;

FIG. 5 is a diagram showing a printed example based on the firstembodiment;

FIGS. 6 and 7 are diagrams explanatory of the first operation mode ofthe system shown in FIG. 1;

FIG. 8 is a flowchart showing a second operation mode of the systemshown in FIG. 1;

FIGS. 9A-9C and 10 are diagrams explanatory of the second operation modeof the system shown in FIG. 1;

FIG. 11 is a flowcharg showing a third operation mode of the systemshown in FIG. 1;

FIGS. 12A-12C are diagrams explanatory of the third operation mode ofthe system shown in FIG. 1;

FIGS. 13A-13C and 14A-14C are diagrams each showing original dotpatterns, printed examples based on the second embodiment, and printedexamples based on the third embodiment, respectively;

FIG. 15 is a diagram showing a printed example based on the thirdembodiment; and

FIGS. 16A-16C are diagrams explanatory of the third operation mode ofthe system shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings. In FIG. 1, 1 is a print character designatingmeans such as a personal computer, 2 is an original dot pattern storagecircuit comprised of a font ROM in which the dot data representative ofa plurality of original dot patterns showing letters, numerals, symbolsand the like is stored, 3 is a RAM for temporarily storing both the dotdata representative of an original dot pattern read from the originaldot pattern storage circuit 2 and the dot data representative of asecondary dot pattern obtained by converting the original dot pattern inaccordance with a given algorithm, 4 is a control circuit for readingthe dot data from the original dot pattern storage circuit 2, convertingthe pattern of the original dot pattern, controlling printing, and soon, and 5 is a printing means comprising a print head or the like forperforming printing on the basis of the dot data stored in the RAM 3.

When high-speed printing is to be performed, a mode switch (not shown)is turned to select a high-speed print mode, and then the printcharacter designating means 1 is operated to designate print characters.Upon designation of the print character, the dot data representative ofan original dot pattern corresponding to the designated print characteris read from the original dot pattern storage circuit 2, the originaldot pattern is converted in pattern in accordance with a given algorithmby the control circuit 4, and is stored in the RAM 3. Then, printing isperformed by the printing means 5 on the basis of the dot pattern storedin the RAM 3.

A first embodiment of the process of converting the pattern of theoriginal dot pattern by the control circuit 4 will now be described withreference to the flowchart of FIG. 2.

Assume that the dot data representative of one dot line of the originaldot pattern, corresponding to the designated character and read from theoriginal dot pattern storage circuit 2, is stored in the RAM 3 indeveloped form as shown in FIG. 3(a) so that the 1st, 5th, 9th . . . dotpositions have individual dots d . . . d. With respect to the dot data,first, a check is made to determine whether or not a dot is present atthe first dot position. When a dot is present, it is retained there.Then, a check is made to determine if dots are present at the subsequenttwo dot positions (5th and 9th dot positions). When a dot is present atat least one of the two dot positions, a dot is generated at the middleposition between the two dot positions. In this way, three dots areconverted into two dots. The foregoing processing is repeated withrespect to subsequent dots, so that the original dot pattern of one dotline shown in FIG. 3(a) is converted into the arrangement of FIG. 3(b)whose dot interval is 1.5 times longer (step 1).

When the pattern of all dot lines is converted entirely, the print headis scanned on the basis of the thus converted dot data at a speed 1.5times faster than usual, so that printing elements such as printingwires are driven at the maximum response frequency of the usual printing(step 2).

In this way, letters and the like designated by the print characterdesignating means 1 are printed at a speed 1.5 times faster than usual.

FIG. 4 shows a printed example based on the original dot pattern, andFIG. 5 shows a printed example based on the secondary dot patternobtained by converting the original dot pattern in accordance with thefirst embodiment.

Although the first embodiment converts the pattern starting with theprocess of retaining a dot there, conversion may be performed startingwith the process of generating a dot at the middle position between twosuccessive dot positions as shown in FIG. 6.

Although the first embodiment converts the pattern in such a manner thatthe first process of retaining a dot as it is and the second process ofgenerating a dot at the middle position between two successive dotpositions are alternated, conversion may be performed in such a mannerthat when one or more dot positions have no dot, a then-appearing dot isretained there, and when at least one of subsequent two dot positionshas a dot, a dot is generated at the middle position between them asshown in FIG. 7.

A second embodiment of the process of converting the original dotpattern by the control circuit 4 will be described with reference to theflowchart of FIG. 8.

Assume that the dot data representative of one dot line of the originaldot pattern is stored in the RAM 3 in developed form as shown in FIG.9(a). With respect to each dot, first, four intermediate dots aregenerated and stored successively (step 1) as shown in FIG. 9(b).

Then, only dots from the intermediate dots that are present at dotpositions spaced from the first dot position by an integral multiple ofa dot interval 1.5 times longer than usual are selected, and the otherintermediate dots are removed. As a result, successive dots from the dotdata representative of one dot line shown in FIG. 9(a) are convertedinto those arranged at dot intervals of 1.5 times longer than usual(step 2). as shown in FIG. 9(c).

When the pattern of all dot lines is converted entirely, the print headis scanned on the basis of the thus-converted dot data at a speed 1.5times faster than usual, so that the printing elements such as printingwires are driven at the maximum response frequency of usual printing(step 3).

In this way, letters and the like designated by the print characterdesignating means I are printed at a speed 1.5 times faster than usual.

A printed example of the secondary dot pattern obtained by convertingthe original dot pattern shown in FIG. 4 in accordance with the secondembodiment is identical with the printed example of the first embodimentshown in FIG. 5.

Although the second embodiment converts the pattern in such a mannerthat only dots out of the intermediate dots that are arranged at dotintervals of 1.5 times longer than usual are selected, conversion may beperformed in such a manner that when no intermediate dot is present atsome successive dot positions as shown in FIG. 10, a then-appearingintermediate dot is retained there, and only dots from the subsequentintermediate dots that are arranged at dot intervals of 1.5 times longerthan usual are selected.

Although the processes described above with reference to FIGS. 9 and 10select dots arranged at dot intervals of 1.5 times longer than usual,dots arranged at dot intervals of 1.25 or 1.75 times longer than usualmay be selected. For example, in FIG. 9, every 5th intermediate dot maybe selected instead of every 6th intermediate dot; in this case, thescanning speed of the print head is increased to 1.25 times faster thanusual so that printing can be attained at a speed 1.25 times faster thanusual. Similarly, every 7th intermediate dot may be selected instead ofevery 6th intermediate dot; in this case, the scanning speed of theprint head is increased to 1.75 times faster than usual so that printingcan be attained at a speed 1.75 times faster than usual.

Although each of the foregoing embodiments converts one dot into foursuccessive intermediate dots, by giving an adequate storage capacity tothe RAM 3, one dot can be converted into n(n≧2) intermediate dots; inthis case, when there are 2n or more successive intermediate dots, byselecting every m{(2n-1)≧m≧(n+1)}-th intermediate dot and increasing thescanning speed of the print head to K(1<K<2) times, preferably K=m/n,printing can be attained at a speed of K times faster.

A third embodiment of the conversion of the pattern of the original dotpattern by the control circuit will now be described with reference tothe flowchart of FIG. 11.

Generally, the maximum response frequency of the printing elements suchas wire pins is determined by the condition that all dots of one lineare successively printed, and the usual scanning speed of the print headis determined such that the character will be printed optimally when theprinting elements are driven at that maximum response frequency.Practically, however, where only two or three successive dots are to beprinted, the printing elements can be driven at a response frequencyhigher than the maximum response frequency. This embodiment is based onthe assumption that the printing means 5 can print the last one ofsuccessive dots, i.e. two successive dots, at a response frequency 1.5times higher than usual, and intends to improve the printing quality bymaking use of the foregoing property.

Assume that the dot data representative of one dot line of the originaldot pattern is stored in the RAM 3 in developed form as shown in FIG.12(a). First, each dot is converted to two successive intermediate dots(step 1) as shown in FIG. 12(b).

Then, the first intermediate dot is selected, and a check is made todetermine whether or not the number x of successive intermediate dotssubsequent to the thus selected dot meets the condition: n≦x≦2n-1 (n isthe number of intermediate dots generated on the basis of one originaldot; n=2 in this example). When the condition is fulfilled, i.e. whenthere is only one dot which can be successively selected, printing canbe performed at a response frequency of 1.5 times higher than usual;therefore, a dot present at a dot position spaced from the first dotposition by the same dot interval as that of the original dot pattern (adot d1 in FIG. 12(c)) is selected. On the other hand, when x≧2n, i.e.when there are two or more dots which can be successively selected,since the usual response frequency is used for driving, intermediatedots present at dot positions spaced from each other by a dot interval1.5 times longer than usual (a dot d2 in FIG. 12(c)) are selected. Inthis way, all dote except the thus selected dots are removed;consequently, the dot data representative of one dot line shown in FIG.12(a) is converted into the arrangement of FIG. 12(c) (step 2).

When the pattern of all dot lines is converted entirely, the print headis scanned on the basis of the thus converted dot data at a speed 1.5times faster than usual, so that the printing elements such as printingwires are driven at the maximum response frequency of usual printing, orat a response frequency 1.5 times higher than the maximum responsefrequency, to attain print (step 3).

In this way, letters and the like designated by the print characterdesignating means 1 are printed at a speed 1.5 times faster than usual.

For illustrative purposes, FIG. 13(a) shows an original dot pattern, (b)shows a secondary dot pattern obtained by converting the original dotpattern (a) in accordance with the second embodiment, and (c) shows asecondary dot pattern obtained by converting the original dot pattern(a) in accordance with the third embodiment. The secondary dot pattern(b) has bold vertical lines as compared with the original dot pattern(because the dot interval is increased to 1.5 times) and its right upperand lower portions are slightly distorted; but, such points are improvedin the pattern (c), or the pattern (c) is closer to the original dotpattern.

Further, FIG. 14(a) shows an original dot pattern, (b) shows a secondarydot pattern obtained by converting the original dot pattern (a) inaccordance with the second embodiment, and (c) shows a secondary dotpattern obtained by converting the original dot pattern (a) inaccordance with the third embodiment. The secondary dot pattern (b) hasdistorted oblique lines as compared with the original dot pattern; but,such points am improved in the pattern (c), or the pattern (c) hassmooth oblique lines as is the case of the original dot pattern.

FIG. 15 shows a printed example of a secondary dot pattern obtained byconverting the original dot pattern shown in FIG. 4 in accordance withthe third embodiment.

Although the third embodiment converts each dot of the original dotpattern to two intermediate dots, as shown in FIGS. 16(a) and 16(b),each dot of the original dot pattern may be converted to fourintermediate dots. In this case, as shown in FIG. 16(c), in response tothe maximum response frequency of the printing elements attained insuccessive dot printing of short period, only dots out of successiveintermediate dots that are present at dot positions spaced from thefirst dot position by an integral multiple of a dot interval 1.25 or1.75 times longer than usual are selected. When the number x ofsuccessive intermediate dots subsequent to the thus selected dot meetsthe condition: n≦x≦2n-1 (n=4 in this example), a dot present at a dotposition spaced from that dot position by the same dot interval as thatof the original dot pattern is selected. Consequently, it is possible toattain printing at a speed 1.25 or 1.75 times faster than usual byincreasing the scanning speed of the print head to 1.25 or 1.75 timesfaster than usual.

Although the third embodiment makes it possible for the printing means 5to print two successive dots at a response frequency higher than theusual maximum response frequency, it is also possible to print three ormore successive dots at a response frequency higher than the usualmaximum response frequency. For this purpose, proper intermediate dotscompatible with such performance will be selected.

Although each of the foregoing embodiments stores the dot datarepresentative of one line in the RAM 3 in developed form, the dot datarepresentative of one character may be stored.

Although each of the foregoing embodiments converts the pattern afterstoring the dot data representative of the original dot pattern in theRAM 3 in developed form, conversion may be performed while the dot datarepresentative of the original dot pattern is being read from theoriginal dot pattern storage circuit 2; in this case, only the dot datarepresentative of the converted dot pattern may be stored in the RAM 3in developed form.

According to the present invention, the printing speed can be increasedwith little deterioration in printing quality. The invention makes itpossible to print the original dot pattern in the form of a dot patterncloser thereto with little degradation of the printing quality.

What we claim is:
 1. A method for printing wherein a printhead issuccessively scanned in a line direction to print a plurality of dotsextending in said line direction and a recording medium is fed at rightangles to said line direction in normal printing mode or high speedprinting mode, selectively, scanning speed of the printhead in thenormal printing mode is V1 and scanning speed of the printhead in thehigh speed printing mode is V2(V1<V2), and minimum driving cycle of theprinting element in the normal printing mode is determined as t1, thoughthe printing element having response characteristics drivable by shorterdriving cycle than the driving cycle t1 only while printingpredetermined number of successive dots, wherein the steps in the highspeed printing mode comprising of:converting original dot patternincluding fonts, graphics and the like, into secondary dot patternhaving dot density lower than that of said original dot pattern;scanning the printhead at the speed V2; printing the secondary dotpattern by the printing element, the driving cycle of the printingelement, in response to the predetermined number of successive dot dataof the secondary dot pattern, being shorter than the minimum drivingcycle t1, and the driving cycle of a printing element, in response toremaining dot data of the secondary dot pattern, being longer than orequal to the minimum driving cycle t1.
 2. A method for printing whereina printhead is successively scanned in a line direction to print aplurality of dots extending in said line direction and a recordingmedium is fed at right angles to said line direction in normal printingmode or high speed printing mode, selectively, scanning speed of theprinthead in the normal printing mode is V1 and scanning speed of theprinthead in the high speed printing mode is V2(V1<V2), and minimumdriving cycle of the printing element in the normal printing mode isdetermined as t1, though the printing element having responsecharacteristics drivable by shorter driving cycle than the driving cyclet1 only while printing predetermined number of successive dots, whereinthe steps in the high speed printing mode comprising of:receivingoriginal dot data representative of an original dot pattern includingfonts, graphics and the like, having individual original dot data;converting the original dot data into secondary dot data for printingsecondary dot pattern having dot density lower than the original dotpattern; arranging the secondary dot data in a buffer memory atpositions for representing the secondary dot pattern; scanning theprinthead at the speed V2; reading out the secondary dot data from thebuffer memory in synchronous with the scanning of the printhead; drivingthe printing element in response to the secondary dot data read out fromthe buffer memory, the driving cycle of a printing element is shorterthan the driving cycle t1 in response to the predetermined number of thesuccessive secondary dot data, and the driving cycle of a printingelement, in response to remaining secondary dot data of the secondarydot pattern, being longer than or equal to the minimum driving cycle t1.